Piston engine could be one of the most popular and important machineries the human ever made. Yet the vibration problem of piston engines is also well-known and detrimental. Among bending and torsional vibration, the later is more pronounce. It results of early failure and low quality of functioning of engine members, which include for example rear flexible coupling, front accessory drive belt, transmission gears, valve timing and finally, the itself crankshaft--the backbone of the engine which handles the entire power output of the engine.